1. Field of the Invention
The present invention generally relates generally to the field of automatic faucets. More particularly, the present invention relates to a capacitive touch on/off controller for automatic residential faucets.
2. Description of the Related Art
Automatic faucets have become popular for a variety of reasons. They save water, because water can be run only when needed. For example, with a conventional sink faucet, when a user washes their hands the user tends to turn on the water and let it run continuously, rather than turning the water on to wet their hands, turning it off to lather, then turning it back on to rinse. In public bathrooms the ability to shut off the water when the user has departed can both save water and help prevent-vandalism.
One early version of an automatic faucet was simply a spring-controlled faucet, which returned to the “off” position either immediately, or shortly after, the handle was released. The former were unsatisfactory because a user could only wash one hand at a time, while the latter proved to be mechanically unreliable.
One solution was the hands-free faucet. These faucets employed a proximity detector and an electric power source to activate water flow without the need for a handle. In addition to helping to conserve water and prevent vandalism, hands-free faucets had additional advantages, some of which began to make them popular in homes, as well as public bathrooms. For example, there is no need to touch the faucet to activate it; with a conventional faucet, a user with dirty hands may need to wash the faucet after washing their hands. In public facilities non-contact operation is more sanitary. Hands-free faucets also provide superior accessibility for the disabled, the elderly, and those who need assisted care.
Although hands-free faucets have many advantages, some people prefer to directly control the start and stop of water, depending on how they use the faucet. For example, if the user wishes to fill the basin with water to wash something, the hands-free faucet could be frustrating, since it would require the user to keep a hand continuously in the detection zone of the sensors.
Thus, for many applications touch control is preferable to hands-free control. Touch control provides a useful supplement to manual control. Typically, faucets use the same manual handle (or handles) to turn the water flow off and on and to adjust the rate of flow and water temperature. Touch control therefore provides both a way to turn the water off an on with just a tap, as well as a way to do so without having to readjust the rate of flow and water temperature each time.
Consequently, some touch-control faucets have been developed, especially for kitchen sink applications. In some cases, the touch control may be as simple as a push-button. In certain faucets, the touch control is implemented using a strain gauge that responds to the impulse from a tap.
Strain gauges, however, have a number of shortcomings. Because they are sensitive to force, rather than actual contact, their response over the period of a given contact is uneven. For example, when a user first makes contact with a touch sensor based on a strain gauge, the initial impulse of contact appears as a substantially magnified force. After the initial contact, the response of the strain gauge is related to other confounding variables, such as the pressure of the contact, and the direction of the applied force.
Since the purpose of a touch-control is to provide the simplest possible way for a user to activate and deactivate the flow of water, the location of the touch control is an important aspect of its utility. The easier and more accessible the touch control, the more effort is saved with each use, making it more likely that the user will take advantage of it, thereby reducing unnecessary water use. Since the spout of the faucet is closest to the position of the user's hands during most times while the sink is in use, it is an ideal location for the touch control. However, in practice it has proved unsuitable, because the spout of a typical kitchen sink is swiveled between the two basins found in most kitchen sinks. With a touch-control positioned in the spout, when the user touches the spout to swing it from one basin to the other (or to otherwise reposition the spout), the faucet is undesirably deactivated (or activated).
The handle of a faucet is another good location for a touch sensor, because the user naturally makes contact with the handle of the faucet during operation.
Another issue with automatic faucets of all varieties is battery life. For both safety and cost reasons many people prefer to use battery power to operate hands-free faucets. Consequently, power consumption is an important design consideration.
Thus, what is needed is touch-control water faucet that can distinguish between contact for the purpose of activating or deactivating water flow and contact for the purpose of swinging the spout from one basin to the other, and which can be operated on standard commercial batteries without having to change the batteries more than once during a typical three-month period. The present invention is directed towards meeting these needs, among others.